In the field of research for pharmaceutical development, during tests, it is necessary to store a large number of samples at low temperature and to analyze them at high efficiency. Therefore, the storage and transportation of a storage rack has been carried out by sealing or encapsulating a sample-dissolved solution in a cylindrical- or a rectangular-tubular small vessel, called a microtube and depositing the microtubes into the storage rack partitioned into the total of 384 wells in a matrix with 16 rows and 24 columns in accordance with a standard of SBS (Society for Biomolecular Screening) (see for example, Japanese Patent Publication No. 2007-33061 (page 6, paragraphs 25 to 26, FIG. 1).
Such a storage rack having the 384 wells in accordance with the standard of SBS has very short well pitch of 4.5 mm. When a removable cap is used for closing open ends of microtubes accommodated into the storage rack, mounting of caps by a machine simultaneously was very difficult. Thus the caps each must be mounted on the tubes and much labor and time have been needed for mounting caps on all open ends of the 384 microtubes in the storage rack.
The present inventors have invented a new method of mounting a cap on the microtube comprising the steps of previously aligning caps of microtubes on an alignment plate with cells having the same pitch as the wells in the storage rack, and overlying this alignment plate on the storage rack. The caps aligned on the alignment plate are pushed into the open tops of the microtubes accommodated in the storage rack, so that the cells overlie the wells of the storage rack. The caps are permitted to be passed through the alignment plate by the resilient compressibility of the cap, so that the open tops of all microtubes deposited in the storage rack are closed with caps simultaneously. The present inventors have developed a cap alignment device for aligning caps on an alignment plate in short time, so as to carry out the above-mentioned method of mounting a cap efficiently (see Japanese Patent Application No. JP2008-46092).